INAUGURAL ADDRESS. 5 



tliey vaty, m a broad sense at least, with the condition of the atom 

 and with its electrical state, with the temperature and the pressure of 

 the gas of which the atom forms part, and so forth. We are staggered 

 by diflficulties of interpretation, and crave for some simple method of 

 attacking the great problem. Spectrum analysis speaks a language 

 Vvhich we barely understand as yet. 



Now you will understand the welcome which we give to a new 

 science like radio-activity, which addresses us in simple phrases. We 

 are here .still concerned with radiations emitted by atoms, either 

 directly or in a secondary sense; and still we try to gain from an 

 examination of the radiations some knowledge of the atoms from 

 v.hich tJio radiations proceed. But we work under totally different 

 conditions. Nothing marks the change moi'e forcibly than the disap- 

 j>earance, complete or almost complete, of all dependence on physical 

 and chemical conditions. The radio-active substances exercise their 

 marvellous powers at a rate which cannot be hastened or delayed by 

 any known agency, such as heat or cold or pressure ; not even if they 

 are made to form chemical compounds with other substances. And, 

 again, when the radiations which they emit pass through material 

 substaucas, and are scattered or absorbed, as we find to be the case, 

 the scattering and absorption are independent of the physical or 

 chemical condition of those substances. We have, as it were, gone 

 below the foundations of physics and chemistry to the simpler primor- 

 dial conditions on which the more complex sciences are built. There 

 are radio-active phenomena which go so far as to take no account of 

 those fundamental distinctions between atoms on which chemistry is 

 basefl. The most penetrating gamma rays, in passing through sub- 

 stances, recognise no other property than that of mass ; four atoms of 

 aluminium affect them no more and no less than one atom of silver, 

 because the former weigh as much as the latter, and the names 

 '' silver " and '" aluminium " no longer convey a distinction. 



It is clear that we are dealing with the most fundamental charac- 

 teristics of the atoms, with the building material, and not with the 

 sti-uctuT-e ; with the inner nature of the atom, and not its outside show; 

 and it is this which differentiates radio-activity from the older 

 sciences. You will remember how Jules Verne in one of his bold flights 

 of imagination drives the submarine boat far down into the depths of 

 the sea. The unrest of the surface, its winds and waves, are soon left 

 behind ; the boat passes through the teeming life below, down into 

 regions wliere only a few strange and lonely creatures can stand the 

 enormous [)re«sure, and, diving still, reaches at last black depths where 

 there is a vast and awful simplicity. Here, where no man " hath come 



